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High Speed Solution Exchange (HSSE-2)
The HSSE-2 (High Speed Solution Exchange System) is a well proven design for rapid solution
exchange (200µs range) for electrophysiological experiments. The system utilizes a four-way
pinch valve to select between 2 channels.
Each channel has up to 4 different solution choices. The high speed exchange is a result
of the close proximity of the two solutions
to the subject. (Usually a dissociated cell attached to a pipette, i.e. whole cell
configuration, or an outside-out, or inside-out patch on an electrode tip.) The pipette
is located within several hundred microns of the two output tubes which face each other at
90° in the same plane. Solution flows over the subject from only one side at a time.
When the four-way pinch valve is switched, solution flow switches from one side to the
other. The new solution, which was in the dormant tube, primed in position, now reaches
the cell in µseconds!
The four-way pinch valve permits fluid not flowing to the subject to be directed to waste. This constant flow keeps fluid in the system fresh, reduces air bubbling and provides momentum to increase the speed of the solution exchanges. The HSSE also has two two-way pinch valves that are used to start and stop the flow to waste when necessary. The two two-way valves and the four-way valve are controlled via a four channel controller called the BPS-4. Each valve can be turned on and off manually or via a TTL signal from a data acquisition system. The voltage supplied to the valves are 12V, and the extra channel can be used to add an additional valve to the system if necessary. Eight solution reservoirs are suspended on a pole for gravity flow. Manual rotary valves select 2 out of the eight solutions for application (1 from 1-4 and 1 from 5-8). Some priming is always necessary when making solution changes to eliminate previous solutions. The front end 90° tubing holder is designed to reach over the wall of a small petri dish and allow the tube ends to be submerged. Actual output velocity is varied by adjusting the reservoir heights Solution reservoirs (A) are divided so that 4 go to rotary valve B1 and 4 to B2. Selected solutions flow to 4-way pinch valve (C) which controls final output as shown to right. Solution not flowing to the prep. is directed to waste. Flow to waste is controlled via pinch valves D1, D2. Optimal 20-80% Response Times: 20µs jump from 150mM to 75mM NaCl across open electrode (junction potential) <50µs jump from 0 to 10mM ACh across outside-out patch from BC3H-1 cells containing muscle-type ACh receptor channels (+50mV) |
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